Welding method

ABSTRACT

A method is proposed for welding a first component part to a second component part, the energy to melt melting regions being supplied by a laser beam. In this context, the laser beam is directed through the first component part, which is made of a nonabsorbing material, to the second component part. The second component part is made of a material which strongly absorbs laser beam. At least one stop is provided outside melting regions.

FIELD OF THE INVENTION

[0001] The present invention is based on a method for welding.

BACKGROUND INFORMATION

[0002] Methods for welding component parts are already known in whichthe welding energy is supplied by a laser. In this context, so-calledtransmission technique welding methods are known in which the laser beamis directed through a transparent component onto a second componentwhich absorbs the laser beam. Because of the absorption, this region isstrongly heated, until melting of the material takes place. When thefused portion gets in touch with the material of the transparentcomponent, this material is also melted, so that welding of the twocomponents takes place. In order to guarantee contact of the fusedportion of the absorbing material with the transparent material, the twocomponents are pressed together during welding. The distance betweenthem is set by measuring the welding path and by regulating the energysupplied, or it sets in after welding as a function of the force used.

SUMMARY OF THE INVENTION

[0003] On the other hand, the method according to the present inventionhas the advantage that the distance between the two components duringwelding is predefined by the stops. The distance between the twocomponents in the welded state is thus not dependent on the force withwhich the two components are pressed together during welding. If the twocomponents are at an angle to each other in the fused region, excessmolten material may be conducted in a defined way to one side of themelting region. In that way, the quality of the welding site isimproved.

[0004] The stops may optionally be designed to be on only one side ofthe welding seam or on both sides of the welding seam. The methodaccording to the present invention is particularly suitable for weldingcomponents to one another which form a housing, especially a housing foran electronic component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIGS. 1 and 2 show a first exemplary embodiment,

[0006]FIGS. 3 and 4 show a second exemplary embodiment,

[0007]FIGS. 5 and 6 show a third exemplary embodiment and

[0008]FIGS. 7 and 8 show a fourth exemplary embodiment.

DETAILED DESCRIPTION

[0009] With the aid of cross sections through the component parts, FIG.1 shows a first exemplary embodiment of the method according to thepresent invention for welding component parts. FIG. 1 shows a conditionbefore welding and FIG. 2 after welding.

[0010]FIG. 1 shows a first component part 1 and a second component part2 in cross section. First component part 1 is particularly thought of asbeing a housing cover, and second component part 2 is particularlythought of as being a housing base. As indicated by force arrow 3, thefirst component part is pressed against second component part 2. Then,in the state at which they are pressed together, laser beams 4 aredirected all the way through component part 1 at component part 2.Component part 1 is made of a material which is transparent to laserbeams, i.e. as good as none, or only a little absorption of energy fromlaser beam 4 takes place in the material of component part 1. Componentpart 2 is made of a material which strongly absorbs laser beam 4. Thisabsorption brings on a strong heating effect, since the energy of thelaser beam is absorbed in a low volume of component part 2. Componentparts 1 and 2 each have melting regions 5. In the case of these meltingregions 5, the regions involved are regions which are molten for theactual welding, i.e. the regions of component parts 1 and 2 whosematerials are mixed with each other by being molten, and thus form theactual welding connection. These regions are denoted as melting regions5, independently of whether before or after the actual welding.

[0011] Plastics are especially considered as materials for componentparts 1 and 2. In the case of such plastics, using appropriateadditives, particularly for laser beams in the infrared range, it may beaccomplished that the one plastic material absorbs as good as none ofthe energy of the infrared laser beam, while the other material stronglyabsorbs the energy of the infrared laser.

[0012] When the laser beams are irradiated into melting regions 5 ofstrongly absorbing component part 2, a great quantity of heat isintroduced into this melting region 5. Therefore, the material of lowercomponent part 2 begins to melt. When this fluid melt comes into contactwith melting region 5 of upper component part 1, upper component part 1is also molten in this melting region 5. This is attained by pressingcomponent parts 1 and 2 together during the welding process, and thusthe molten material of lower component part 2 comes in contact withupper component part 1. Small gaps possibly still in existence arebridged by capillary forces. By melting the materials of component parts1 and 2 in melting regions 5, this brings on a thorough mixing andfinally the development of the actual welding connection. This weldedjoint 7 is shown in cross-section in FIG. 2. By the welded joint 7 thusdeveloped, component part 1 and component part 2 are firmly connected toeach other. If welded joint 7 is designed as a circumferential weldingseam, a hermetically sealed connection of component parts 1 and 2 iscreated. In particular, component part 2, which is here designed as ahousing base, may have a large recess 11, in which components to bepackaged before welding, particularly electronic switching circuits, maybe positioned.

[0013] If, during welding, component parts 1, 2 are pressed against eachother using sufficiently great force, molten material is expressedsideways from welding regions 5. Thus, depending on force 3, thegeometric form of welded joint 7 and thus also the distance between thetwo component parts 1, 2 in the welded state will vary. According to thepresent invention, it is therefore proposed that stops 6 be providedwhich limit the movement of the two component parts 1, 2 during weldingin the direction of force 3. In FIGS. 1 and 2, stops 6 are created by acorresponding stepwise design of first component part 1 and of secondcomponent part 2, the stepwise projections being dimensioned so that,before welding, component parts 1 and 2 first rest upon one another inmelting regions 5. Then, when the laser energy is irradiated intomelting regions 5, a little of the molten material is displacedsideways, and the stepwise stops come to lie on each other. Then, aftercooling, component parts 1 and 2 lie on stops 6 which lie next towelding connections 7. Stops 6 are situated geometrically next tomelting regions 5, so as to make sure that the laser irradiation willnot cause a softening of stops 6 and thus, possibly, deformability inthese areas.

[0014] An additional exemplary embodiment of the method according to thepresent invention is explained in FIGS. 3 and 4. Reference numerals 1,2, 3, 4, 5, 7 and 11 denote again the same objects as in FIGS. 1 and 2which also fulfill the same functions. However, in contrast to FIGS. 1and 2, in FIGS. 3 and 4 a larger number of stops 6 is provided. In thiscontext, in particular, stops 6 are situated not only on one side ofmelting regions 5 but on both sides of melting regions 5. In the outerregions, stops 6 are provided which are situated directly next towelding regions 5. In the middle region of component parts 1, 2 anadditional central stop 6 is provided, which is positioned relativelyfar from melting regions 5. On account of this central stop 6, inparticular, deformation of component part 1 is limited during thewelding procedure. This is especially meaningful if components 1 and 2form a housing in which the hollow spaces 11 enclosed therein have alarge lateral expansion. In that case, the first component part 1 isdesigned as a cover which also has a great lateral expansion. Comparedto lateral expansion, component part 1, which forms the cover, isdesigned relatively thin in its thickness. By introducing force 3 duringthe welding procedure, a deformation of component part 1, which formsthe cover, may therefore come about, and component part 1 would againtake on its original shape after welding, when force 3 is no longeracting upon component part 1. Thus, mechanical stresses would begenerated in component part 1 which would place a load on the weldingconnection. Since the deformation of component part 1 during welding islimited in the middle region by stop 6, mechanical stresses in thefinished housing are also lowered by this measure.

[0015]FIGS. 5 and 6 show another exemplary embodiment of the methodaccording to the present invention. Reference numerals 1, 2, 3, 4, 7 and11 denote again the same objects as in the previous figures which alsofulfill the same functions. However, one difference comes about here bythe design of molten regions 5 and stops 6. As may be seen in FIG. 5,component part 1 is designed simply as a plate-shaped component elementhaving plate surfaces which have no structuring. Second componentelement 2 has a melting region 5 which has a certain elevation comparedto stops which are situated in the immediate closeness to melting region5, on both sides of melting region 5. The height of this elevation isillustrated in FIG. 5 in an exaggerated manner, and depends in realityessentially on to what depth laser beams 4 melt the material of secondcomponent part 2. FIG. 6 shows a cross section through the finishedwelded component, where it should be realized that first component part1 essentially lies flat on the plane which was formed in FIG. 5 by stops6 of component part 2. Welded joints 7 extend, starting from this plane,slightly into component parts 1 and 2. The advantage of the methodaccording to FIGS. 5 and 6 is the simple embodiment of first componentpart 1, which, in particular, may be designed as a simple plate.

[0016]FIGS. 7 and 8 show another exemplary embodiment of the methodaccording to the present invention. Reference numerals 1, 2, 3, 4, 5, 6,7 and 11 denote again the same objects as in FIGS. 1 and 2 which alsoexercise the same functions. However, in contrast to FIG. 1, meltingregion 5 of component part 2 is not designed to be parallel to meltingregion 5 of component part 1, but is at an angle to it. By this angle isachieved that molten material of lower component part 2 and of uppercomponent part 1 is displaced sideways toward the outside in a definedmanner by the pressing together of component parts 1, 2. This is madeclear in FIG. 8 by welding material drops 12, which are squeezed outsideways from welded joints 7 during welding. By the beveling of meltingregion 7 of component part 2, a preferred exit of excess molten materialin the lateral direction was effected.

[0017] Naturally, it is also possible to design both melting regions 5,i.e. both on component part 1 and on component part 2, to be beveled,particularly so that they do not form a right angle with the directionof force 3. The lateral expulsion of molten material is thereby boostedeven more. Further more, this form of embodiment of melting region 5makes sense even without the formation of stops 6, since, by the beveledmelting regions of component parts 1, 2 that have not yet been welded,in any case a sideways exit of excess molten material is ensured.However, both measures, i.e. stops 6 and beveled design of meltingregions 5 contribute to improving the quality of the welding ofcomponent parts 1 and 2. This is to be desired particularly in the fieldof packaging electronic components, since in that field very strictrequirements are placed on the quality of a welded joint for a housingfor an electronic component.

1-7. (Canceled)
 8. A method for welding a first component part to asecond component part, comprising: causing a laser beam to supply anenergy to melt melting regions of the first component part and thesecond component part, the first component part being made of a materialthat only weakly absorbs the energy of the laser beam, and the secondcomponent part being made of a material that strongly absorbs the energyof the laser beam; directing the laser beam all the way through thefirst component part to the second component part; pressing the firstcomponent part and the second component part against each other from apoint of welding taking place; and providing outside the melting regionsat least one stop by which a movement of the first component part andthe second component part toward each other is limited.
 9. The method asrecited in claim 8, wherein: the melting regions are designed in such away that a welded joint is formed after cooling, as an elongated weldseam.
 10. The method as recited in claim 9, further comprising: formingthe at least one stop on one side of the weld seam.
 11. The method asrecited in claim 9, wherein: the at least one stop includes at least afirst stop and a second stop, the first stop is provided on one side ofthe weld seam, and the second stop is provided on another side of theweld seam.
 12. A method for welding a first component part to a secondcomponent part, comprising: causing a laser beam to supply an energy tomelt melting regions of the first component part and the secondcomponent part, the first component part being made of a material thatonly weakly absorbs the energy of the laser beam, and the secondcomponent part being made of a material that strongly absorbs the energyof the laser beam; directing the laser beam all the way through thefirst component part to the second component part; pressing the firstcomponent part and the second component part against each other from apoint of welding taking place; and angling the first component part andthe second the component part to each other in the melting regionsbefore welding, so that, during welding, a preferred exit of moltenmaterial on one side of the melting regions is effected.
 13. The methodas recited in claim 8, wherein: in the welded state, a housing iscreated by the first component part and the second component part. 14.The method as recited in claim 13, wherein: the housing is for anelectronic component.
 15. The method as recited in claim 12, wherein: inthe welded state, a housing is created by the first component part andthe second component part.
 16. The method as recited in claim 15,wherein: the housing is for an electronic component.
 17. The method asrecited in claim 8, wherein: the first component part and the secondcomponent part include a plastic, and different absorption propertiesare set by addition of further substances to the plastic.
 18. The methodas recited in claim 12, wherein: the first component part and the secondcomponent part include a plastic, and different absorption propertiesare set by addition of further substances to the plastic.